public class ASPxDataValidationEventArgs :
    ASPxGridDataValidationEventArgs

Public Class ASPxDataValidationEventArgs
    Inherits ASPxGridDataValidationEventArgs

using DevExpress.Web.ASPxGridView;
using System.Collections.Generic;

protected void grid_RowValidating(object sender, 
DevExpress.Web.Data.ASPxDataValidationEventArgs e) {
    // Checks for null values.
    foreach (GridViewColumn column in grid.Columns) {
        GridViewDataColumn dataColumn = column as GridViewDataColumn;
        if (dataColumn == null) continue;
        if (e.NewValues[dataColumn.FieldName] == null)
            e.Errors[dataColumn] = "Value cannot be null.";
    }
    // Displays the error row if there is at least one error.
    if (e.Errors.Count > 0) e.RowError = "Please, fill all fields.";

    if (e.NewValues["ContactName"] != null && 
        e.NewValues["ContactName"].ToString().Length < 2) {
        AddError(e.Errors, grid.Columns["ContactName"], 
        "Contact Name must be at least two characters long.");
    }
    if (e.NewValues["CompanyName"] != null && 
    e.NewValues["CompanyName"].ToString().Length < 2) {
        AddError(e.Errors, grid.Columns["CompanyName"], 
        "Company Name must be at least two characters long.");
    }
    if (string.IsNullOrEmpty(e.RowError) && e.Errors.Count > 0) 
    e.RowError = "Please, correct all errors.";
}

void AddError(Dictionary<GridViewColumn, string> errors, 
GridViewColumn column, string errorText) {
     if(errors.ContainsKey(column)) return;
     errors[column] = errorText;
 }

protected void grid_HtmlRowPrepared(object sender, 
ASPxGridViewTableRowEventArgs e) {
    // Checks whether the generated row has the errors.
    bool hasError = e.GetValue("ContactName").ToString().Length <= 1;
    hasError = hasError || e.GetValue("CompanyName").ToString().Length <= 1;
    hasError = hasError || e.GetValue("Country") == null;
    // If the row has the error(s), its text color is set to red.
    if (hasError)
        e.Row.ForeColor = System.Drawing.Color.Red;
}

protected void grid_StartRowEditing(object sender, 
DevExpress.Web.Data.ASPxStartRowEditingEventArgs e) {
    // Validates the edited row if it isn't a new row,.
    if (!grid.IsNewRowEditing)
        grid.DoRowValidation();
}

Imports DevExpress.Web.ASPxGridView
Imports System.Collections.Generic

Protected Sub grid_RowValidating(ByVal sender As Object, ByVal e As 
DevExpress.Web.Data.ASPxDataValidationEventArgs)
    ' Checks for null values.
    For Each column As GridViewColumn In grid.Columns
        Dim dataColumn As GridViewDataColumn = TryCast(column, GridViewDataColumn)
        If Not dataColumn Is Nothing AndAlso_ 
        (e.NewValues(dataColumn.FieldName) Is Nothing) Then
            e.Errors(dataColumn) = "Value cannot be null."
        End If
    Next column
    ' Displays the error row if there is at least one error.
    If e.Errors.Count > 0 Then
        e.RowError = "Please, fill all fields."
    End If

    If Not e.NewValues("ContactName") Is Nothing AndAlso_
    e.NewValues("ContactName").ToString().Length < 2 Then
        AddError(e.Errors, grid.Columns("ContactName"),_
        "Contact Name must be at least two characters long.")
    End If
    If Not e.NewValues("CompanyName") Is Nothing AndAlso_
    e.NewValues("CompanyName").ToString().Length < 2 Then
        AddError(e.Errors, grid.Columns("CompanyName"),_
       "Company Name must be at least two characters long.")
    End If
    If String.IsNullOrEmpty(e.RowError) AndAlso e.Errors.Count > 0 Then
        e.RowError = "Please, correct all errors."
    End If
End Sub

Private Sub AddError(ByVal errors As_
    Dictionary(Of GridViewColumn, String), ByVal column As GridViewColumn,_
    ByVal errorText As String)
     If Not errors.ContainsKey(column) Then
     errors(column) = errorText
     End If
End Sub

Protected Sub grid_HtmlRowPrepared(ByVal sender As Object,_
ByVal e As ASPxGridViewTableRowEventArgs)
    ' Checks whether the generated row has the errors.
    Dim hasError As Boolean = e.GetValue("ContactName").ToString().Length <= 1
    hasError = hasError OrElse e.GetValue("CompanyName").ToString().Length <= 1
    hasError = hasError OrElse e.GetValue("Country") Is Nothing
    ' If the row has the error(s), its text color is set to red.
    If hasError Then
        e.Row.ForeColor = System.Drawing.Color.Red
    End If
End Sub

Protected Sub grid_StartRowEditing(ByVal sender As Object,_
    ByVal e As DevExpress.Web.Data.ASPxStartRowEditingEventArgs)
    ' Validates the edited row if it isn't a new row,.
    If (Not grid.IsNewRowEditing) Then
        grid.DoRowValidation()
    End If
End Sub